1. Field of the Invention
The present invention relates to a method for manufacturing powdery crystalline maltitol.
2. Description of the Prior Art
Maltitol has been utilized as a sweetening agent in low-calorie foods, diet foods, low cariogenic foods and foods for diabetic patients since it will not be easily digested and absorbed in the human digestive canal and also not easily fermented by oral bacteria.
However, maltitol has been inconvenient in handling since its dried products are extremely hygroscopic, deliquescent and difficult to powder.
With a view to overcoming this problem, a number of techniques have been proposed for implementing the crystallization or powderization of maltitol.
More specifically, for example, a method was disclosed in Japanese Patent Publication No. 2439/1988, in which seed crystals are added into a highly concentrated maltitol solution for crystallizing out anhydrous crystalline maltitol. This method characterized in that a high purity crystalline maltitol can be obtained, but it gives only low yield, showing low workability.
Japanese Patent Publication No. 11599/1990 and Japanese Patent Laid-Open Publication No. 180795/1986 proposed methods in which maltitol obtained by hydrogenation of maltose is submitted to chromatography for increasing purity and then crystalline maltitol is separated from the concentrated solution of this purified maltitol. The methods, however, are also problematic in regard to yield and workability.
A method was disclosed in Japanese Patent Laid-Open Publication No. 268696/1986, wherein a mass consisting of maltitol syrup and crystals is made to flow through a gradient crystallizing-out zone the temperature of which has been lowered and the separated crystals are collected. A large-sized apparatus is required and payability is low.
According to Japanese Patent Publication No. 7349/1991, seed crystals are added to a highly concentrated maltitol solution at a high temperature, and after adjusting the moisture content to 2-15% by weight, the mixture is gradually cooled so as to solidify the maltitol, and the solid is roughly broken, as required, followed by drying, and thereafter powderized into desired particle sizes, thus making maltitol products as a commodity. In this method, an aqueous solution of 70% maltitol is concentrated to 4% of moisture content and, after powdery maltitol is added thereto, the mixture is cooled from 90.degree. C. to room temperature over about 20 hours for solidification. No description is given on application of shearing force for the solidification. In this method a long time is required for the solidifying and crystallizing processes and a large amount of energy is required for cutting and pulverizing the solid matter there obtained.
Japanese Patent Publication No. 47140/1989 disclosed a method, wherein a concentrated solution of hydrogenated maltose is placed in a tray and crystals are added and the mixture, after thoroughly kneaded, is kept hot for allowing crystallization to proceed and plasticity to appear, and thereafter the product is extruded through nozzles, followed by cooling, and cut into granular maltitol. This method also requires a long time for crystallization and a great amount of energy for cutting solidified maltitol.